Most patients with acute myeloid leukemia (AML) are incurable using standard therapy (Mrozek et al, 2012, J Clin Oncol, 30:4515-23) and those with relapsed or refractory AML (RR-AML) have a particularly poor prognosis (Kern et al, 2003, Blood 2003, 101:64-70; Wheatley et al, 1999, Br J Haematol, 107:69-79).
Genetic engineering can impart to T cells specificity toward a target of choice. T cells can be transduced with genetic material encoding a single chain variable fragment (scFv) of an antibody, in conjunction with a signaling molecule, thereby using the complementarity determining region (CDR) to recognize a cell surface antigen in a non-MHC restricted manner. These cells are termed chimeric antigen receptor (CAR) T cells. Preclinical and clinical attempts to target at least 20 different surface molecules in a variety of malignancies have shown some activity yet were often limited by poor persistence of the infused CAR T cell product (Sadelain et al, 2009, Curr Opin Immunol 2009, 21:215-23). Recent success with anti-CD19 redirected T cells in patients with advanced CLL and ALL (Porter et al, 2011, N Engl J Med, 365:725-33; Kalos et al, 2011, Science Transl Med, 3:95ra73; Grupp and Kalos, 2013, N Engl J Med, 368:1509-18) demonstrated that these cells can eradicate massive tumor burden after a single infusion with remission lasting up to 3 years to date, underscoring the dramatic potential of CAR T cell therapy. There have been few preclinical attempts to target AML in animal models (Marin et al, 2010, Haematologica, 95:2144-52; Tettamanti et al, 2013, Br J Haematol, 161:389-401) although a recently published small clinical trial demonstrated that it is feasible to produce and infuse T cells to patients with an aggressive malignancy (Ritchie et al, 2013, Mol Ther, 21:2122-9). Besides the ability for the chimeric antigen receptor on the genetically modified T cells to recognize and destroy the targeted cells, a successful therapeutic T cell therapy needs to have the ability to proliferate and persist over time, and to further monitor for relapse. T cells may be variably efficacious due to anergy, suppression or exhaustion but skilled practitioners have limited control over these features at this time. To be effective, CAR transformed patient T cells need to persist and maintain the ability to proliferate in response to antigen. It has been shown that ALL patient T cells perform can do this with CART19 comprising a murine scFv (see, e.g., Grupp et al., NEJM 368:1509-1518 (2013).